Cured-in-place pipe repair (CIPP) has been used to repair damaged main sewer pipes or lateral sewer pipes as well as other types of conduits. Generally, a liner tube is impregnated with a resinous material, and is positioned in a pipe adjacent a damaged area of pipe. The liner tube is pressed against the wall of the damaged area of the pipe and the resin is allowed to cure, thus leaving a renewed pipe wall. In addition, the liner tube is either pulled in place or inflated and inverted into the pipe to the damaged area in need of repair.
Liner tubes are generally formed from a flat piece of material, which is sized to be the correct length and width to fully cover the lateral pipe wall. The material is then rolled together, with the two ends of the width of the liner connected by stitching or welding, to form the tube. The diameter of the liner tube must be the same as the diameter of the lateral pipe. If the liner tube has a diameter less than the diameter of the lateral pipe, ripping or tearing of the liner could occur. If, on the other hand, the liner tube has a diameter greater than the diameter of the lateral pipe, the liner tube may fold over itself, or create bulges in the cured liner. These folds or bulges could cause blockages in the lateral pipe, and would need to be cut or sanded out. The extra work would be time consuming and expensive.
At times, lateral pipes have varying diameters along their lengths. The variable diameter pipes require custom liners to be constructed. A first length of tubular liner will be formed to repair a length of the pipe having a certain diameter, and a second length of liner will have to be formed to line up with the section of the pipe having the second diameter. To repair the pipes, either the liners will be positioned and cured separately, or at the same time. A problem exists in either method, however. It is important to have the right diameter of liner tube for the appropriate section of pipe, with the change in diameter of the liner tube corresponding to the exact location of the change in diameter of the pipe. If this is not the case, the above-mentioned problems of tearing or folding will occur.
As lateral pipes may be lengthy, it has been difficult to accurately determine both the location of the change in diameter of pipe, as well as the value of the change. Therefore, there is a need in the art for a method and means of determining the location of and amount of change in a lateral pipe diameter. There is also a need to determine the information as quickly as possible to be able to efficiently repair the wall of the pipe.